Automatic telephone system



March 30,1943. w. T. POWELL 2,315,378

AUTOMATIC TELEPHONE SYSTEM Fi'ld Sept. 13, 1940 10 Sheets-Sheet 1 INVENTOR.

Wl/VFZED 72' POWELL A ORNEY.

30, 1943. w. 'r. POWELL 2,315,378

AUTOMATIC TELEPHONE SYSTEM V Filegi Sept. 13, 1940 1Q Sheets-Sheet 2 I?I INVENTOR.

WIN/2E0 7: POM Ell ATTORNEY.

- March 30, 1943.

POWELL AUTOMATIC TELEPHONE SYSTEM Filed se tnls, 19 1b 1 .O Sheets-Sheet3 "A I OR-NEY.

March 30, 1943. w. POW L 2,315,378 v I I AUTOMATIC TELEPHONE SYSTEMFiled Sept. 13, 1940 10 Sheets-Sheet 4 l J H I i LINE H l we T r .m 1731 27.4

I T I175 l L A l 208 207 I am y l 3 n I v l 3 205 I EN. i Bill/5N. M 04206 (-n H INVENTOR.

W/IVFEED 7'. POWELL A ORNEY.

March 30, 1943.

W. T. POWELL Filed Sept. 13, 1940 AUTOMATIC TELEPHONE SYSTEM 10Sheets-Sheet 5 Wl/VFPED 7'. POWELL ATTORNEY.

March 30, 1943.

Filed Sept 1 w. T., POWELL AUTOMATIC TELEPHONE SYSTEM 15, 1940 10Sheets-Sheet 6 1 mvmom W/NFEED Z POWELL 30,1943. w. -T, aws; 2,315,378 IAUTOMATIC TELEPHONE SYSNTEM Filed Sept. 13, 1940 1 o Sheets-Sheet v IEEV. 2/176 TONE I 63 a) m,-1 I I isY l "ATTORNEY.

March so, 1943. I w.1". POWELL JJ {2,315,378 AUTOMATIC TELEPHONE SYSTEM"'Fil'ed Sept}. 13. 1940 10 She ets-Sheet s D/FFEPENT/FL INVENTORQW/NFEED Z" POW n .8 F 42% I AI*ORNEY.

March 30, 1943. v w, 1', p 'wE 2,315,378

AUTOMATIQ TELEPHONE SYSTEM Filed Sept. 13, 1940 l0 Sheets-Sheet 9INVENTOR.

W/NFRED r POWLL A ORNEY.

March 1943- w. r. POWELL 2,315,378

AUTOMAT IC TELEPHONE SYSTEM Filed Sept. 13, 1940 10 Sheets-Sheet l0INVENTOR. 1 [0 WM/Fem z POWELL BY A I A ZTTORNEY.

Patented Mar. 30, 1943 AUTOMATIC TELEPHONE SYSTEM Winfred T. Powell,Rochester, N. Y., assignor to The Stromberg-Carlson TelephoneManufacturing Company, Rochester, N. Y., a corporation of New YorkApplication September 13, 1940, Serial No. 356,623

6' Claims.

This invention relates to telephone systems and more particularly toautomatic telephone systems.

Present automatic telephone systems, are commonly so arranged that it isnecessary for the calling party when calling another subscriber on hisown line to dial a difierent number from that by which the wanted partythereon is usually called. Such an arrangement for handling revertivecalls is confusing to the subscriber and results in many false calls.

In accordance with the present invention, a novel arrangement isprovided wherein certain means discriminates between an ordinary busyline and a busy line due to a revertive call thereon while dialing thesame called line number in the case of a revertive call as in the caseof. a normal call. This discriminating means in the first instanceprevents the signalling of the'busy wanted line but in the secondinstance permits the wanted subscriber, in the case of the revertivecall, to be signalled during the period that the calling subscribertemporarily hangs up his receiver in accordance with instructions.

Another feature of the invention relates to an arrangement whereby aseries of counting relays in addition to effecting the selectingoperation of the connector also selectively controls the application ofselective ringing current to the called subscribers line.

Still a further feature of the invention relates to a novel arrangementfor intercepting preliminary impulses.

The various features and advantages of the invention will appear fromthe detailed description and claims when taken with the drawings whichdiagrammatically represent the automatic telephone system of the presentinvention, when ar ranged with Figs. 1, 2, 3 and 4 in a horizontal rowand with Figs. 5, 6, 7, 8, 9 and 10 arranged in a second horizontal rowin the, order named, the upper margins of Fig. 5 matching with the lowermargin of Fig. 1. In Figs. 1 and 5 there is illustrated a callingtelephone line and the lockout arrangement common to a group oftelephone lines; Figs. 2 and 6 represent a group of finder relays forconnecting a link circuit to a calling telephone line; Figs. 7, 8 and 9illustrate a link circuit and the counting relays associated therewith;the righthand portion of Fig. 9 and Fig. 10 illustrate a relay connectorfor connecting a link to a wanted telephone line; Figs. 3 and 4represent a trunking arrangement whereby a call maybe extended to orreceived from a trunk connected to a distant office.

It is believed that the inventionwill best be understood by describingthe operations involved in extending a telephone call from a callingsubscribers substation #221 to a called subscribers substation #214.When the calling subscriber at substation #221 originates a call byremoving his receiver from its switchhook, a circuit is completed forthe line'relay II] from the negative pole of battery, upper winding ofthis relay, back contact and armature of the cutoff relay I I, upperside I2 of the calling subscribers line thru the calling subscriberssubstation network, lower side of the calling subscribers line l3, lowerwinding of the relay Ill, lower back contact and armature of the cutoffrelay II, to the positive pole of battery. In the form of the systemherein disclosed, there is provided a lookout relay arrangement wherebyonly one callingsubscriber at a time can extend his line to an idle linkcircuit. This locking relay arrangement comprises twenty tens lockoutrelays (of which only ten are completely illustrated, the twentieth tensrelay being shown in dotted lines) and ten units lockout relays. Whenthe line relay III is energized, a lockout circuit is completed from thenegative pole of battery, resistance 26,,continu-- ity and back contactof relays/TI to TIU inclusive, conductor I5, back contact, continuityspring and winding of the second tens lockout relay I6,

conduotor II, innermost back contact and armature of the slow releasingrelay I8, armature and front contact of the linerelay Ill, middle arma--ture and back contact of relay I8, conductor 20, the first units lockoutrelay 2I, continuity spring and back contact of this relay, conductor22, back contact and continuity spring of relays UIU to UI inclusive, tothe positive pole of battery. The tens lockout relay i6 and the unitslockout relay 2| are operated over the above described circuit, each ofwhich closes a locking circuit for itself and opens the operatingcircuit for the others in the corresponding group. Thus the tens relayI6 and the units relay 2i are locked operated until the callingline isextended to an idle link circuit. It will be understood that whilethetens relay and the units relay are, operated, no other tens or unitsrelays cangbe operated,

since their energizing circuits will be interrupted by the tens lockoutrelay and the units lockout relay then operated.

Alarm relay I4, which is normally energized except when a call is beingextended by the lockout relays, functions whendeenergize-d to close analarm circuit. This alarm circuitlbecomes efiective when the relay I4 isdeenergized for a period longer than that normally necessary to extend acalling line to a link. Alarm relay 23 functions in like manner inconnection with the units lockout relays to close an alarm circuit whenan operated one of these relays fails to release Within a short intervalof time.

As soon as the tens lockout relay l5 and the units lockout relay 2| havebeen energized and locked operated in the manner just described, thetens finder relay and the units finder relay of an allotted link circuitfunction to connect this allotted link to the calling line. Let it beassumed that the first link of this series is allotted for use and underthis condition the slow releasin allotter relay 2'! is operated from thenegative pole of battery, winding of this relay, upper back contact andarmature of the relay 28, conductor 29, front contact and armature 35 ofthe units lockout relay 2!, conductor 3|, armature 32 and front contactof the tens lockout relay It, to the positive pole of battery. As soonas the allotter relay 21 operates, it closes an energizing circuit forth relay 33 from the negative pole of battery, winding of this relay,upper front contact and armature of the relay 2? and thence overconductor 29 and the remainder of the circuit just described, to thepositive pole of battery at the armature 32 and front contact of therelay It. When the relay 33 attracts its armatures it completes anenergizing circuit from the negative pole of battery, units finder relay54, conductor 35, front contact and armature 35 of the relay 33,outermost armature and front contact of units lockout relay 2|, to thepositive pole of battery. Relay 34 is energized in this circuit.Similarly, the #2 tens finder relay 3'! is energized in a circuittraceable from the negative pole of battery, winding of this relay,conductor 58, front contact and armature 35 of relay 53, conductor 45,armature 4| and front contact of tens lockout relay It to the positivepole of battery. When the finder relays 54 and 3'! are thus operated,the tip ring and sleeve conductors respectively designated 42, 43 and 45are extended thru the armatures of the finder relay 31, conductors 45,45 and 47, thence thru the armature and front contacts of the unitsfinder relay 34 to the tip, ring and sleeve conductors 45, 45 and 55 ofthe selected link circuit. These tip and ring conductors 48 and 49 arethus connected in series with the calling line and thru the armaturesand back contacts of the relay 5|, the continuity springs and backcontacts of the relay 52, thru the upper and lower windings in series ofthe battery feed and impulse relay 53, to the positive pole and thenegative pole of battery, respectively. The impulse relay 53 is thusenergized and completes a circuit from the negative pole of battery,winding of the slow release relay 54, front contact and armature ofrelay 53, uppermost back contact and armature of the relay 5|, to thepositive pole of battery. As soon as the slow releasing relay 54 isoperated, it completes a locking circuit for the tens finder relay 3'!and the units finder relay 34. This locking circuit is completed fromthe positive pole of battery, back contact and continuity spring of therelay 55, conductor 55, middle armature and front contact of relay 54,conductor 5", armature and front contact and winding of units finderrelay 34 to the negative pole of battery and in multiple therewith thruthe armature, front contact and winding of the tens finder relay 3'! tothe negative pole of battery. Also when the slow releasing relay 54 isoperated, it closes an energizing circuit for the slow releasing relay58 from the negative pole of battery, winding of this relay, lowermostarmature and front contact of relay 54, to the positive pole of battery.Also as soon as the slow releasing relay 54 is energized, it appliesbusy potential to the sleeve conductor 50 of the link. This busypotential is applied from the positive pole of battery, back contact andcontinuity spring of the relay 59, middle armature and front contact ofthe relay 54, to the sleeve conductor 55 of the link. It will beunderstood that this busy potential prevents the calling line from beingseized by any other line.

When the slow releasing relay 58 operates, it applies positive potentialat its upper armatures and front contacts to the holding conductor 60and thence thru a branch 52 of this conductor, back contact andcontinuity spring of the relay 5|, conductor 63, lower Winding of theallotter relay 28 to the negative pole of battery. The allotter relay 28on operation closes a locking circuit for itself from the negative poleof battery, front contact and upper winding of this relay, conductor 64,back contact and armature of the relay 55, associated with the lastallotter relay of the series, to the positive pole of battery. It willbe appreciated that as a result of this last-described circuit, theallotter relay 28 of link #1 and similar allotter relays of theremaining links of the series will operate and remain locked until thelast allotter relay of the series, namely relay 280 is energized, atwhich time the previously lockedallotter relays of the series willrelease. This arrangement insures that the links ar used in rotation.

Further, when the slow releasing relay 58 operates, it applies a dialingtone, from the dial tone source, front contact and armature of relay 58,conductor 55, inner back contact and armature of relay 51, conductor 68,lower winding of the battery feed relay 52, to the negative pole ofbattery. Dial tone current in this circuit is repeated over the linkcircuit in use and over the calling subscribers line where it is heardas a dial tone in the receiver of the calling subscriber. This dial toneindicates to the calling subscriber that the apparatus is in readinessto receive the several series of code impulses corresponding to thecalled subscribers substation.

It has been assumed that the designation of the called subscriberssubstation is #214, therefore the calling subscriber operates his dialsender to transmit two impulses corresponding to the hundreds digit ofthis line. In response to the first impulse, the impulse relay 53 willretract its armature momentarily. This completes a circuit from thepositive pole of battery, uppermost armature and back contact of relay5|, armature and back contact of impulse relay 53, upper armature andfront contact of slow releasing relay 54, conductor 59, armatures andback contacts of the busy relay It and the cut-in relay Tl conductor 72,winding of the slow releasing change-over relay l3 to the negative poleof battery. It will be understood that the changeover relay as well asthe slow-releasing relay 54, fall to respond to the momentary operationsof the impulse relay 53. When, however, at the conclusion of each seriesof impulses, the impulse relay is held operated for a considerableperiod of time, slow releasing change-over relay is will release. Asecond circuit in multiple with the energizing circuit of thechange-over relay 13 is completed from the negative pole of battery,upper winding of the relay i4, uppermost back contact and armature ofthe relay l5, conductor I6 and thence over conductor 12 and theremainder of the circuit just described, to the positive pole of batteryat the back contact and the armature of relay Thus when the impulserelay 53 retracts its armature in response to the first impulse of thehundreds digit, the changeover relay I3 and the relay 14 are bothenergized. With the relay 14 energized, it closes a second circuit foritself which incidentally is ineffective at this time. This secondcircuit extends from the negative pole of battery, upper Winding of therelay 14, its upper armature and front contact, lower winding of therelay 15, innermost lower front contact and armature of relay 13, andthence over the holding conductor Gil to the positive pole of battery atthe front contact and armature of the relay 58. This last describedcircuit is ineffective as long as the armature of the impulse relay 53is retracted in response to 'the first impulse, since there is positivepotential present on the conductor it which serves to shunt out thelower winding of the relay 15. However, when the impulse relay 53attracts its armature at the conclusion of the first impulse, thispositive potential will be removed from the conductor 75, so that therelay M will be locked operated, and the relay 15 will be energized inthe circuit which was previously described as ineffective. With relaysi4 and 75 both operated, the number one counting relay H is operatedfrom the negative pole of battery, winding of this relay, thru the backcontacts and armatures of counting relays i8, 88, 82, 84 and 86,conductor 3'5, middle front contact and armature of relay is, frontcontact and armature of relay 75, front contact and armature ofchange-over relay 73, holding conductor 6| to the positive pole ofbattery. It should be mentioned that as soon as the change-over relay 13operates, it completes an operating circuit for the relay 88 from thenegative pole of battery, resistor 89, lowermost armature and frontcontact of change-over relay 13, winding of the relay 88, holdingconductor 6|! to the positive pole of battery. As soon as the number onecounting relay is energized, it closes a locking circuit for itself fromthe negative pole of battery, winding of this relay, its innermost frontcontact and armature, innermost back contacts and armatures of relays Hto 86 inclusive, conductor 9|], middle armature and front contact ofrelay 88 to the positive pole of battery over the holding conductor 68.When now the impulse relay 53 retracts its armature again in response tothe second impulse of the hundred digit, the lower winding of the relayM is energized from the negative pole of battery, lower winding of thisrelay, its front contact and armature, uppermost front contact andarmature of relay l5, conductors E6 and 12, back contacts and armaturesof relays H and i0, conductor 69, front contact and armature of relay54, back contact and armature of the impulse relay 53, back contact andarmature of relay 5|, to the positive pole of battery. At this time boththe upper and lower windings of the relay M are energized and since thisrelay is differentially wound, it retracts its armatures. However, therelay i5 is maintained operated until the close of the second impulse,from the negative pole of battery thru its upper winding, front contactand armature to the positive pole of battery over conductors i6 and i2as previously described. However at the close of the second impulse withthe relays M and iii deenergized and with the number one counting relay11 operated, the

number two counting relay 18 is energized from the negative pole ofbattery, winding of this relay, front contact and armature SI of relay11 back contacts and armatures of relays I4 and 15, front contact andarmature of change-over relay 13, to positive potential on the holdingconductor 80. The number two counting relay 18 looks itself operatedfrom the negative pole of battery, winding of relay 18, its inner frontcontact and armature, innermost back contacts and armatures of relays 19to 86 inclusive, conductor 90, middle armature and front contact ofrelay 88, to positive pole of battery over holding conductor 69.

At the conclusion of the hundreds series of impulses, the change-overrelay l3 retracts its armatures and at its lowermost armature andcontinuity spring, it opens the original energizing circuit of the relay83. However, the relay 88 is slow releasing and before it releases itcompletes a circuit for itself from the positive pole of battery on theholding conductor 60, winding of the relay 88, continuity spring andback contact of the change-over relay 13, front contact and armature 92of relay B6, armatures and back contacts of the transfer relays 93, 94and 61, conductor 95, armature 96 and front contact of the number twocounting relay 18 (now energized), winding of the hundreds relay 91, tothe negative pole of battery. Relay 88 as well as the relay 91 areenergized in this circuit and the relay 91 closes a locking circuit foritself from the negative pole of battery, its winding, armature andfront contact, conductor 98, winding of the relay 6?, conductor 99,continuity spring and back contact of relay 5|, branch 62 of the holdingconductor Ell, to the positive pole of battery. The transfer relay 6'!is not energized in this circuit since it is shunted at this time by abranch circuit 98a of the conductor 98, back contact and armature ofrelay 61, front contact and lowermost armature of relay 38 to theholding conductor fill. The slow releasing relay 88 is shunted in acircuit from the holding conductor 6% through the winding of relay 88,back contact and continuity spring of the change-over relay 13, frontcontact and armature 92 of relay 88, armatures and back contacts ofrelays 93, 94 and 61, conductor 95, armature 96 and front contact ofrelay 1B, armature and front contact of relay 9?, conductors Q8 and 98a,back contact and armature of relay 61, lower front contact and armatureof relay 88 and thence to positive potential over the holding conductor60. Shortly after the completion of this shunt circuit the relay 8%releases and at its lower armature and front contact it removes thepreviously described shunt circuit about the relay 6T. Relay 6? thenattracts its armatures. The apparatus is now in condition to receive theimpulses corresponding to the tens digit which in the present instanceis assumed to be one.

In response to the single impulse of the tens series, the impulse relay53 retracts its arma ture. When this takes place, the relay 14 isenergized from the negative pole of battery, its winding, back contactand armature of the relay I5, conductors 16 and 12, back contacts andarmatures of relays 1| and 10, conductor 69, front contact and armatureof the relay 54, back contact and armature of the impulse relay 53, tothe positive pole of battery at the back contact and armature of therelay 5|. The changeover relay 13 is also energized in multiple with thelast-mentioned circuit, as previously described. As soon as thechange-over relay operates, it closes an energizing circuit from thenegative pole of battery, resistor 89, armature and front contact of thechange-over relay l3, winding of the relay 88 to ground over the holdingconductor Bil. As soon as the relay T4 is energized in the mannerdescribed, it closes a circuit thru its upper winding, its armature andfront contact, lower winding of the relay I5, front contact and armatureof change-over relay 13 to ground over the holding conductor 66. Thislast-mentioned circuit is ineffective, since it is shunted by theoriginal energizing circuit of relay l i, which circuit includes theconductor 16, as long as the impulse relay 53 retracts its armature inresponse to the single tens impulse. However, at the close of thisimpulse, impulse relay 53 attracts its armature and opens this shuntcircuit, whereupon the mentioned circuit of relays 14 and 75, which hadpreviously been ineffective, now holds the relay M operated and operatesthe relay '55. With relays i i and t 0-perated, an energizing circuit isclosed for the number one counting relay ll extending from the negativepole of battery, winding of this relay, back contacts and armatures ofrelays T8, 80, 82, 84, and 86, conductor Bl, front contacts andarmatures of relays M and 15, front contact and armature of thechange-over relay 73 to the positive pole of battery over the holdingconductcr $8. It will be understood that the change-over relay, which isslow releasing, remains energized for a short interval but soon retractsits armatures after its energizing circuit is interrupted at thearmature and back contact of the impulse relay 53, when this last-namedrelay attracts its armature at the conclusion of the tens series ofimpulses. The number one counting relay ll when operated, closes alocking circuit for itself from the negative pole of battery, itswinding, front contact and armature, back contacts and armatures ofrelays 18 to 86 inclusive, conductor 90, armature and front contact ofrelay $38, to the positive pole of battery over the holding conductor60. It will be recalled that the relay 9'! was operated and lockedoperated in response to the hundreds impulses. Now with the number onecounting relay 1! operated and locked operated in response to the tensseries of impulses, a circuit is completed for operating the tens relayHit! of the relay connector associated with the link in use. The relay!90 is energized in a circuit traceable from the negative pole ofbattery, winding of this relay, conductor liii, front contact andarmature m2 of the counting relay ll, conductor I03, front contact andarmature E94 of the relay 9?, conductor #85, uppermost front contact andarmature of relay iii, back contacts and armatures of relays 94 and Q3,armature 92 and contact of relay 88, continuity spring and back contactof change-over relay [3, winding of the relay 88 to the positive pole ofbattery over the holding conductor 68. The tens connector relay I00,when operated, closes a locking circuit for itself from the negativepole of battery, winding of this relay, its front contact and armature,conductor E95, winding of the relay 94, to the positive pole of batteryover the holding conductor 60. The relay use is locked operated in itscircuit but the relay 94 does not operate at this time since it isshunted by a circuit extending from conductor I06 thence over conductorI01, inner back contact and armature of relay 94, front contact andarmature of relay 61, front contact and armature of relay 88, conductor60 to the positive pole of battery. It will be understood that thisshunt circuit is effective as long as the relay 88 is operated. However,the slow releasing relay 88 is shunted at this time and shortlyafterwards retracts its armatures. This shunt circuit may be traced fromthe positive pole of battery connected to the conductor 60, winding ofthe relay 88, back contact and continuity spring of the change-overrelay 13, front contact and armature 92 of relay 88, armatures and backcontacts of relays 93 and 94, armature and front contact of relay 6! toconductor I05, armature H34 and front contact of relay 97, conductor i33, armature and front contact of relay Tl, conductor IGI, front contactand armature of relay H30, conductor Hi6, winding of relay 94 and againto the positive potential connected to the holding conductor 60. A shortinterval after the relay 88 is thus short circuited it retracts itsarmatures and at its lower armature and front contact interrupts theshunt circuit that had previously existed about the winding of theswitching relay 94. The switching relay 94 is now operated and attractsits armatures. Also as soon as the relay 88 deenergizes it opens thelocking circuit including the conductor which has been holding thecounting relay 1'! operated, thus this relay deenergizes and theapparatus is in condition to receive the impulses corresponding to theunits digit of the wanted numher.

It has been assumed that the units digit of the wanted number is 4 andtherefore the calling subscriber operates his dial sender to transmitfour impulses. In response to each of these impulses, the impulse relay53 retracts its armature. On the first retraction of the armature of theimpulse relay, the change-over relay (3 as well as the relay M areenergized as previously described. When the change-over relay is thusoperated it closes a circuit for again energizing the slow releasingrelay 88. Also when the relay 14 is operated, it closes an ineffectivecircuit as before described thru the upper winding of relay [4, itsarmature and front contact, lower winding of relay 15, front contact andarmature of relay F3 to positive potential over the holding conductor59. Now, when the impulse relay 53 attracts its armature at the close ofthe first impulse, relay l' i will remain energized and relay 3'5 willbe operated. Therefore, the number one counting relay 7? will beoperated as before described from the ne ative pole of battery, windingof this relay, back contacts and armatures of relay 78, 8G, 82, 84 and86, conductor 81, front contacts and armatures of relays 14 and 15,front contact and armature of the change-over relay 1-5" to the positivepole of battery over the holdconductor 60. Relay 11, when operated,closes a locking circuit for itself thru its innermost front contact andarmature and thence thru the back contacts and armatures of remainingcounting relays, conductor 90, armature and front contact of relay 88;to the positive pole of battery over the holding conductor 60. Inresponse to the second impulse of the units series, the lower winding ofthe relay 14 will be energized from the negative pole of battery, innerfront contact and armature of the relay M, upper front contact andarmature of the relay 15, conductors 18 and 1 2 to the positive pole ofbattery thru the back contact and-armature of the relay 53. It will benoted that the relay [4 is differentially wound and thus when both ofits windings are energized, it will retract its armatures. At the upperarmature and front contact of this relay, the energizing circuit thruthe lower winding of the relay 15 is interrupted but relay 15 is nowheld operated through its upper winding, front contact and armature overconductor 16. When the impulse relay 53 attracts its armature at theclose of the second impulse of the units series, the locking circuitthru the upper winding, front contact and armature of the relay 15 isinterrupted so that the relay l also retracts its armatures. When thistakes place the number two counting relay is energized from the negativepole of battery, winding of this relay, front contact and armature 9| ofrelay i1, back contacts and armatures of relays M and I5, front contactand armature of change-over relay 13 to positive pole of battery overthe holding conductor 60. In response to the third impulse of the unitsseries, relays M and 15 are operated as previously described, afterwhich the number three counting relay i9 is energized from the negativepole of battery, winding of this relay, front contact and armature ofrelay 18, back contact and armatures of relays 80, 82, 84 and 86,conductor 81, frontcontacts and armatures of relays M and i5, frontcontact and armature of relay i3, conductor 60 to the positive pole ofbattery. Relay 19 onvoperation closes a locking circuit for itself thruits front contact and armature, backv contacts and armatures of relays80 to 86 inclusive, conductor 96, armature and front contact of relay 88to the positive pole of battery over the holding conductor 60. Inresponse to the fourth impulse of the units series, the relay 14 willretract its armatures and when the impulse relay 53 attracts itsarmature at the conclusion of the fourth impulse, the relay 15 will alsoretract its armature. Thereupon the number four counting relay 81B isoperated from the negative pole of battery, winding of this relay, frontcontact and armature of relay 19, back contacts and armatures of relaysM and 75, front contact and armature of change-over relay 13 to thepositive pole of battery on the holding conductor 60. Relay 8!) whenoperated, closes a looking circuit for itself through its own frontcontact and armature and thru the back contacts and armatures of theremaining counting relays of the series, conductor 90 to the positivepole of battery on holding conductor 69 through the armature and frontcontact of relay 88, as previously described. 7

At the close of the units series of impulses when the impulse relay 53holds its armature attracted, the change-over relay l3 deenergizes.Thereupon the units connector relay N38 is operated from the negativepole of battery, winding of this relay, conductor 159, front contact andarmature Hi3 of the number four counting relay B6, conductor ill,uppermost front contact and armature of relay J l, back contact andarmature of relay $3, armature 92 and front contact of relay 88, backcontact and continuity spring of chan e-over relay 73, winding of theslow releasing relay 88 to positive pole of battery over the holdingconductor Eli. The connector relay le on operating, closes a lockingcircuit for itself from negative pole of battery, winding of this relay,its front contact and armature, conductor H2, winding of the relay 93,to the positive pole of battery over the conductor 56. The relay 33 isnot operated at this time, since it is shunted by a circuitincludingconductor H2, conductor H3, back contact and armature cuit.

of the relay 93, front contacts and armatures of relays 94 and 61, frontcontact and armature of relay 88, to the holding conductor 60. However,the slow releasing relay 88 is also shortcircuited by the operation ofthe units connector, relay I08 and shortly afterwards retracts itsarmature so that the relay 93 will be operated. The mentioned shortcircuit for the relay 88 extends from the holding conductor 60, windingof the relay 88, back contact and continuity spring of the change-overrelay I3, front contact and armature 92 of relay 88, back contact andarmature of relay 9-3, armature and front contact of relay fi l,conductor l I l, armature H0 and front contact of the counting relay 80,conductor 109, front contact and armature of relay l 08, conductor I l2,winding of relay 93 and again to the holding conductor 66. Relay 88thereupon releases and by so doing, removes the short circuit about therelay 93, which then operates.

Since the connector relays Hill and H18 have been operated, the linkcircuit in use is connected to the tip ring and sleeve conductors of thecalled subscribers line. The testing of this line now takes place. Ifthis line is idle, positive potential will be absent from its sleeveconductor H4 and therefore the busy test relay 10 will not operate.Consequently, no busy tone will be transmitted to the calling subscriberand he will therefore know that he can now operate his dial sender totransmit impulses for selecting the proper ringing frequency to signalthe desired calling substation on the telephone line to which hissubstation has been connected. It will be noted in the presentarrangement, that provision is made for selectively signalling anyone often substations on a called telephone line. purpose five differentringing frequencies namely sixteen, thirty, forty-two, fifty-four andsixty-six cycle ringing current are provided. Let it be assumed thatsixty-six cycle ringing current will signal the wanted substation.Therefore the calling subscriber operates his dial sender to transmit aseries of five impulses to select that frequency. In response to thefirst impulse the changeover relay i3 is operated and remains operatedduring the series of impulses. Also in response to the five mentionedimpulses, the counting relays for numbers 1 to 5 inclusive, designatedTI to 8|, inclusive, are first energized and then deenergized when thesucceeding relay in the series operates. Consequently. only the #5counting relay 8! remainsoperated. As soon as the change-over relay [3is operated, it closes an energizing circuit for the relay 838 whichcircuit extends from the negative pole of battery, resistor 89, armatureand front contact of change-over relay T3, winding of the relay 88 tothe positive pole of battery over the holding conductor 60. 93 isoperated as previously described, a circuit is closed for the ringingrelay l l 5 from the negative pole of battery, resistor HE, winding ofthe relay I I5, back contact and armature of the cutin relay H, frontcontacts and armatures of relays 93, 94 and 61, front contact andarmature of relay 83, to the positive pole of battery over the holdingconductor Bil. The ringing relay H5 when operated, closes a lockingcircuit for itself thru its innermost front contact and armature overthe holding conductor 59 to the positive pole of battery. The ringingrelay H5 when operated also closes at its uppermost armatures and frontcontacts break points in the link cir- After the change-over relayreleases but For this When the transfer relay before the slow releasingrelay 88 deenergizes, a circuit is completed for operating the cut-inrelay H. This circuit is traceable from the negative pole of battery,lower winding of this relay, back contact and armature H? of the relayH8, conductor IE9, front contact and armature of relay 83, armature 92and front contact of relay 88, back contact and continuity spring ofchange-over relay I3, winding of relay 88 over the holding conductor 60to the positive pole of battery. With the cut-in relay II operated, asecond pair of break points is closed in the link circuit. Since thecounting relay 8| has been operated, 66 cycle ringing current is appliedthru the front contact and armature I20 of relay 8|, back contacts andarmatures of relays 89, I3, 18 and T2, winding of the trip relay I2I,back contact and armature of the reversing relay I22, conductor I23,front contacts and armatures of the ringing relay H and cut-in relay II,tip conductor I24 of the link and thence over the tip conductor of thecalled telephone line, thru the substation ringer of the wantedsubstation, ring conductor of the called telephone line, ring conductorI25 of the link, front contacts and armatures of the cut-in relay II,ringing relay H5, conductor I26, armature and back contact of relay I22.to the generator return. It should be pointed out that the operation ofthe cut-in relay II and the ringing relay H5, closes a circuit thrutheir front contacts and armatures I21 and I28 for starting the ringinggenerator. It should be noted that in the present instance, thereversing relay I22 was not operated since the number of impulses in theringing series of impulses was less than six. If however, the number ofimpulses in the ringing series was six or more, the reversing relay I22would have been operated so that the ringing current would have beenapplied to the ring side of the line. This enables the ten difierentsubstations on a telephone line to be selectively signalled with the useof only five different cycles of ringing frequency, five connectedbetween the tip line to ground and five connected from the ring side toground. It will be appreciated that when the number of impulses in theringing series is six or more, the reversing relay I22 will be operatedfrom the negative pole of battery, its winding, continuity spring andback contact, front contact and armature of the transfer relay 93,armature and front contact of relay '88, conductor I29, front contactand armature I 3!! of the number five counting relay 8|, back contactsand armatures of relays M and I5, inner front contact and armature ofthe change-over relay I3 and thence to the positive pole of battery overthe holding conductor 89. Thus when any of the counting relays 82 to 86inclusive ar selected, the proper one of the five different cycles ofringing frequency will be selected, but in this instance the selectedfrequency will be applied to the ring side of the called telephone line.

When the subscriber at the called station responds by removing hisreceiver from its switchhook, the marginal trip relay i2I will beoperated. At the armature and front contact of the trip relay, a shuntcircuit is completed about the ringing relay H5 which deenergizes toclose one pair of break points in the called end of the link circuit.The telephone connection is now completed, the talking battery beingsupplied to the calling party thru the windings of the impulse relay 53and the talking battery being supplied to the called substation thru thewindings of the relay 52.

At the conclusion of the conversation when the calling subscriberreplaces his receiver on its switchhook, th impulse relay 53 willrelease. Shortly afterwards, the slow releasing relay 54 deenergizes andopens the circuit which has been holding the finder relays operated.Shortly after the release of relay 54, the slow releasing relay 58deenergizes. When this relay releases, it removes positive potentialfrom the holding conductor 60 so that all of the operated relays of thelink circuit will be restored to normal.

Let it be assumed that the called telephone line was busy at the timewhen it was tested. Under this condition the busy relay #0 is energizedfrom the negative pole of battery, winding of this relay, back contactand armature of the relay 93, sleeve conductor I M to the positive poleof battery which is maintaining the called telephone line busy. Relay'Iil when operated, locks itself operated thru innermost lower armatureand front contact over the holding conductor 6t. Also prior to theenergization of the transfer relay 93, the relay H8 will be operatedfrom the negative pole of battery, winding of this relay, armature andfront contact of the busy relay I8, back contact and continuity springof relay 93, to the positive pole of battery over the holding conductor60. Relay I I8 will be released when relay 93 opens the above describedoperating circuit. This is because the locking circuit for relay I is isopen at the lower back contact of relay 59. The operation of relay 59will be described later.

Provision is made for releasing a link circuit in the event that acalled subscriber on a revertive call does not answer or in the eventthat the calling subscriber does not hang up when the called subscriberreplaces his receiver on the switchhook, which would otherwise hold thelink circuit if the calling subscriber maliciously failed to hang up atthe conclusion of the call with the intent of tying up the calledsubscribers line. A timing circuit arrangement for effecting this resultis shown at the bottom of Fig. 3 and at the lefthand portion of Fig. 7.In this timing arrangement, when the relay 52 (Fig. 7) is deenergizedand the relay 58 energized, the timing relay is energized in a circuittraceable from the negative pole of battery, winding of relay 23I (lowerpart of Fig. 3), conductor 232, armature and back contact of relay 52,front contact and armature 233 of relay 58, winding of slow releasingrelay 55, its continuity spring and back contact, conductor 234,armature and back contact of relay 235, armature and back contact ofslow releasing relay 236, back contact and armature of slow releasingrelay 231 to the positive pole of battery. Relay 55 when thus operated,locks itself operated in series with the relay 23I over the conductor232, winding of relay 55, its lower front contacts and armatures,conductor 238, back contact and armature 236 to the positive pole ofbattery. As soon as the relay 23I is energized, it closes an obviousenergizing circuit for the slow releasing relay 233 and this relay atits armature and front contact, closes a circuit for the motor (notshown) which alternately opens and closes the contacts 259. Thesecontacts are arranged to be closed for 2 minutes and opened for 2seconds. As soon as contacts 240 are closed, an obvious circuit iscompleted for the relay 235. This relay at its lower armature and frontcontact completes a multiple circuit which maintains the slow releasingrelay 239 operated so that the motor will continue to run. Also when therelay 23I operates, it completes a circuit for operating theslow-releasing relay 231 from the negative pole of battery, winding ofthis relay, middle front contact and armature of relay 23!, frontcontact and armature of relay 235 to the positive pole of battery. Relay231 then locks itself operated thru the inner front contact and armatureof relay 23i When the relay 235 deenergizes at the close of a 2 minuteinterval the relay 236 is energized in a circuit traceable from anegative pole of battery, winding of this relay, front contact andarmature of relay 231, back contact and armature of relay 235 to thepositive pole of battery. When the relay 236 operates, it opens at itsuppermost armature and back contact a looking circuit which has beenmaintaining the relay 55 operated. The relay 55 then deenergizes toeffect the release of the link. The deenergization of this lookingcircuit also removes positive battery from conductor 51't0 effect therelease of the tens and units finder relays of Fig. 2 for disconnectingthe calling line from the link. This effects the release of cut-01frelay H, after which line relay in is operated by the closed circuit ofthe calling line. Relay l closes a circuit for locking relay I8, beforethis latter relay is released by its deenergization when relay I! wasreleased. With relays l0 and I 8 energized, the circuit to the commonlock-out relays is maintained open, thus preventing the seizure of alink until the calling party disconnects and again initiates a call.

Revertivc call In the event that the called line is found busy at thetime of the busy test, due to the fact that the calling line and thecalled line are one and the same, in other words, a revertive call,provision is made in the present system for handling such a call. Itwill be remembered that at the time the busy test is made, the busy testrelay i6 is operated and thru its innermost, lower front contact andarmature, it closes a locking circuit for itself over the lockingconductor 50. It will further be remembered that this test of the busyline is eifected before the transfer relay 93 (Fig. 9) is energized.During this interval the relay H8 will be operated from the negativepole of battery, winding of relay H8, front contact of relay Ill,conductor 220, back contact and continuity spring of relay 9.3, branchconductor 22! and the holding conductor 60 to the positive pole ofbattery. The operation of relay H8 at its armature 222 and back contact,interrupts the circuit thru the upper wind-- ing of relay 59 which haspreviously maintained this relay energized. With the armature 2'22 andthe front contact of relay H8 closed, a circuit is completed from thepositive pole of battery, holding conductor 60, armature 222 and frontcontact of relay 1 I8, branch conductor 223, sleeve conductor H4 of thelink which is now connected to the sleeve conductor of the called linethru the operation of the connector relays. Since the sleeve conductorH4 is connected to the sleeve conductor of the called line, it will alsobe connected to the sleeve conductor of the calling line inasmuch asthey are branches of the same conductor, thence thru the sleeveconductor which is extended by the finder relays to the sleeve conductor50 of the link in use, armature 224 and front contact of relay 54,continuity spring and armature of relay 59, lower winding of this relayto the positive pole of with the link in use is restored.

battery. Thus the lower winding of the relay 59 is included in a shuntcircuit and since the circuit thru its upper winding has beeninterrupted, this relay releases. When now the transfer relay 93 isoperated as previously described, the relay H8 will have a lockingcircuit completed for itself from the negative pole of battery, windingof this relay, lowermost back contact and armature of relay 59, frontcontact and armature of relay H8, conductor 225, front contact andcontinuity spring of relay 93, branch conductor 22| and holdingconductor 60 to the positive pole of battery. It will be noted that atthe time of the operation of the relay H8, the normal energizing circuitfor the cut-in relay i! is interrupted at the back contact and armaturell! of the relay H8. Thus ringing current is not applied to the calledline at this time. However, the calling subscriber who is making arevertive call is instructed in the directions of his telephonedirectory or otherwise, that when he receives a busy signal on theoccasion of calling a subscriber on his own line, he shall replace hisreceiver on its switchhook for an interval long enough to permitsignalling current to be applied to the called line to signal the calledsubscriber. Thus when the calling subscriber hangs up, the impulse relay53 will be deenergized and shortly thereafter the slow releasing relay54 will release. The release of the relay 54 interrupts the holdingconductor 51 which has maintained the finder switching relays of thelink operated, so that these relays are restored but the calling lineconnection to the link in use is not interrupted since it is now by wayof the connector relays. When the slow releasing relay 54 releases, acircuit is completed for the upper winding of the cut-in relay H. Thiscircuit is traceable from the positive pole of battery, armature 226 andfront contact of relay H8, upper winding of the relay H, continuityspring and back contact of the relay 52', lowermost back contact andarmature of relay 5d. winding-of the slow releasing relay 58, to thenegative pole of battery. Thus when the relay 54 releases, the cut-inrelay TI is operated and the slow releasing relay 53 is continuedoperated to maintain, at its upper armatures and front contacts,positive potential on the holding conductor 56. With the cut-in relay Hoperated break points are closed in the link conductor I24 and so thatthe selected ringing current is applied over this end of the link to thecalled subscribers line. When the calling or called party responds, thetrip relay i2! is energized as previously described and completes acircuit including the conductor 99 which shunts the ringing relay H5.The release of the relay H5 closes another pair of break points in thelink conductors E24 and l25 and at the same time disconnects ringingcurrent from the link circuit. On the response of the called subscriber,the re lay 52 (Fig. '7) is energized and its continuity spring and backcontact interrupts the circuit which has been maintaining the cut-inrelay H and the slow releasing relay 58 energized. When the relay 5%releases, it interrupts at its upper mest armatures and front contactsthe holding conductor 55 so that the apparatus associated Thus thecommon equipment employed thus far in the connection including thefinder relays of the link as well as the link and the connector relaysare restored to normal. On the release of the link from this connection,the cutoff relay H of the calling subscriber (Fig. 6), which is alsocommon to the line of the called subscriber, deenergizes and talkingbattery is then supplied for this revertive call line thru the windingsof the line relay Ill. It should be noted that after the link circuit isreleased as above set forth, a second link circuit is not connected tothe calling line. It ill be seen that while the cutoff relay II isenergized, the slow releasing relay I8 is operated from the negativepole of battery, winding of this relay, front contact and armature ofcut oif relay l I to the positive pole of battery. When however, thecut-off relay II is released in the manner just described, the linerelay I will again be operated thru the called subscribers substation.With the line relay Ill operated the slow releasing relay I3 ismaintained operated from the negative pole of battery, winding of thisrelay, its innermost front contact and armature, front contact andarmature of line relay I8; middle armature and front contact of slowreleasing relay it, winding of the relay 230 to the positive pole ofbattery. Relay 235 closes a lamp circuit indicating that a revertivecall is in process so that in the event that the lamp circuit is lightedfor an abnormal period, an attendant can investigate to find out whetheror not the system is functioning properly. It will be recalled that theinner and middle armatures and back contacts of relay I8, controls thelockout circuit which includes the tens relay I6 and the units relay 21.These relays when operated control the association of a link circuitwith the calling line and since this lockout circuit is interruptedduring a revertive call, no link circuit is associated with this line.

On the conclusion of this revertive call when both subscribers replacetheir receivers, the line relay Iii will deenergize and the equipmentthat has been used in this call will all be restored to normal inreadiness for a succeeding call.

Call from dial office to distant manual ojfice Referring to Fig. 3, whenthe connector relays of a link in use, select a two-way trunk circuit, acircuit is closed from the calling line and this link across theconductors I50 and I5I to operate the relay I52. This relay closes anobvious circuit for operating the relay I53. Relay I53 completes acircuit for operating the relay I54 from the negative pole of battery,winding of this relay, conductor I55, front contact and armature ofrelay I53 to the positive pole of battery Relay I53 on operation alsoapplies positive battery to the allotter conductor I51 for making thistrunk busy and also applies positive battery to the sleeve conductor I58of the trunk for operating relay 5I (Fig. 8), of the link. Furthermore,the operation of relay I53 at its upper armature and back contact opensthe circuit of the normally energizing ringing relay lEI, to permit thisslow releasing relay to deenergize but not until the slow releasingrelay I5! is operated. The joint action of relays I54 and Isl applies animpulse of ringing current to the primary windings of the repeatingcoil. I52 for the purpose of applying a short impulse or" ringingcurrent over the two sides of the trunk leading to the distant manualoflice. This impulse of alternating current is effective to operate thealternating current relay I63 (Fig. 4) which closes a circuit foroperating the relay I64. This circuit is traceable from the negativepole of battery, winding of the slow releasing relay I64, back contactand armature I65 of relay I68, back contact and armature Itl of relayI68, conductor IE9, armature and front contact of relay I53, backcontact and continuity spring of relay I54 to the positive pole ofbattery. Relay IM on operating closes a locking circuit for itselfindependent of the control of the alternating current relay I53. Thiscircuit extends from the negative pole of battery, winding of relay IM,back contact and armature I10 of relay S66, armature and continuityspring of relay I54 to the positive pole of battery. Relay Iii-'1 whenoperated, closes a circuit at its front contact and armature I12 forlighting the incoming or line lamp I13 which indicates to the manualoperator at the distant manual office that a call is awaiting extensionon this trunk, At the close of the impulse of alternating current, thealternating current relay I53 releases but the slow releasing relay I64has been operated and looked as previously described. When the operatoranswers by inserting an answering plug P into the jack J of the trunk onwhich the call is waiting extension, relay I66 is energized in a circuitfrom the negative pole of battery, winding of this relay, uppermostcontact and armature of relay 68, back contact and armature I14 of relayI64, conductor I15, jack contacts I16 (now closed), to the positive poleof battery. Relay 566 when operated, closes a locking circuit for itselffrom the negative pole of battery, its winding, uppermost back contactand armature of relay I68, innermost contact and armature of relay I 66,to the positive pole of battery over conductor i15 as previouslydescribed. The operation of relay I65 opens the locking circuit for theslow releasing relay I64, which circuit is now interrupted at the backcontact and armature I1il of relay I53. Since the relay I64 is slowreleasing, there will be a short interval during which an impulse ofalternating current is transmitted back to the trunk to operate alternating current relay I86 (Fig. 3). This is effected by the operationof the relay I11 which is energized in a circuit closed from thenegative pole of battery, winding of this relay, armature and frontcontact of the ringing relay I18, conductor I19, front contact andarmature I10 of relay I86, armature and front contact of relay I64 tothe positive pole of battery. When after a short interval the slowreleasing relay I64 releases, it interrupts the circuit just describedand relay I11 releases. Also the release of the relay I54 opens thepreviously described circuit for the line lamp I155 which is thusextinguished. On the insertion of the plug P into the jack J, the relayI is energized from the positive pole of battery, winding of themarginal relay I8I, winding of the relay I 38, conductor I82, sleevecontacts of the jack and plug, conductor I83, through the coil I84 andresistor I85 in multiple, to the negative pole of battery. However, theoperation of the relay I88 at this time performs no function on thisclass of call, since the marginal relay I85 does not operate in serieswith the resistance of the coil I84 and the resistor I85,

The operation of the alternating current relay I85 in response to theimpulse of alternating current transmitted back over the trunk in themanner just described, effects the operation of the slow releasing relay81 in an obvious circuit. The energization of relay l5? completes anenergizing circuit for the relay 53% in multiple with the slow releasingrelay I5 1. This circuit extends from the negative pole of battery,Winding of the relay I89, front contact and armature of relay I81,conductor I55, armature and front contact of relay I53, to the positivepole of battery.

At the termination of this impulse of alternating current, the relaysI86, I 81 and I89 release in sequence. When the relay I81 releases, therelay I90 is operated in a circuit from the negative pole of battery,winding of this relay, inner front contact and armature of relay I89,back contact and armature of relay I81, conductor I55, front contact andarmature of relay I53 to the positive pole of battery. Relay I90 whenthus operated, closes a locking circuit for itself through its lowerfront contact and armature, back contact and armature of relay I81 andthence to the positive pole of battery as previously described. Thus therelay I90 remains energized after the relay I89 deenergizes.

The manual operator is now connected to the calling party and afterobtaining the number of the wanted party extends the connection" to thewanted line in the usual manner by signalling the subscriber thereon (bymeans not shown), after which conversation takes place.

At the conclusion of the conversation when the calling subscriber hangsup, the relays I52, I53 and I54 release in sequence. The release ofrelay I53 opens the circuit including the sleeve conductor I58 of thelink circuit in use which operation is effective to release the cut offrelay II of the calling line, as well as the relay of the link. Therelease of relay 5I efiects the release of the tens and units finderrelays. As soon as the relay I53 deenergizes, it closes a circuit foragain operating the ringing relay I6I. As soon as this ringing relayoperates and before the switching relay I54 releases, an impulse ofalternating current is transmitted forward over the trunk as adisconnect signal. This impulse of alternating current causes the. relayI63 (Fig. 4) to operate and release. The operation of the relay I63completes an operating circuit for the relay I9I extending from thenegative pole of battery at the common coin box tone key I92, lowerwinding of relay I9I, front contact and armature I65 of relay I66, backcontact and armature I61 of relay I68, armature and front contact ofrelay I63, back contact and continuity spring of relay I64 to thepositive pole of battery. Relay I9I on operation closes a lockingcircuit for itself from the negative pole of battery through its upperwinding, its inner front contact and armature, conductor I92, armatureI93 and front contact of relay I66, back contact and armature of relayI66, back contact and armature I14 of relay I64, conductor I15, jackcontacts I16, to the positivepole of battery. The operation of the relayI9I includes condensers I94 and I95 in the conductors leading to therepeating coil circuit which is efiective to release the supervisoryrelay (not shown) of the cord circuit at the manual ofiice, for givingthe operator disconnect supervision. When the operator disconnects byremoving the plug P from the jack J, relays I66, ISI and I 80 release.The busy lamp I95 continues to be lighted as long as this trunk is inuse, since its circuit is closed. when the operator answers but isopened by the release of relay I66 when the operator disconnects.

Call from the manual ofiice to the dial ojfice On the initiation of acall from the manual ofiice to the dial office, the operator inserts acalling plug similar to P into the jack J. This causes the relay I60 tobe energized in series with the marginal relay I8I as previouslydescribed. However, the marginal'relay I8I does not operate at thistime. The relay I68 (Fig. 4) is next energized from the negative pole ofbattery, Winding of this relay, back contact and armature ofrelay I66,back contact and armature I14 of relay I64, conductor I15, jack contactsI16 to the positive pole of battery. The operation of relay I68 causesthe slow-operate and slow-release ringing relay I18 to release and inthe interval before the relay I18 releases, the relay I11 is operatedfrom the negative poleof battery, Winding of this relay, conductor 200,armature and front contact of relay I18, front contact and armature ofrelay I58 to the positive pole of battery. With the relay- I11 operated,at its front contacts and armatures, it applies generator current tothe-trunk for operating the relay 201 through the rectifying bridgenetwork RB (Fig. 3). Relay 20 I completes a circuit for operating therelay 202 in a circuit from the negative pole of battery, winding ofthis relay, inner front contact and armature of relay 20I to thepositive pole of battery. In addition, the relay 20I applies positivepotential to the allotter conductor I51 which makes the calling end ofthe trunk busy. Relay 202 completes a circuit for operating the slowreleasing relay 203 which circuit is traceable from the negative pole ofbattery, winding of this relay, back contact and armature of slowreleasing relay 204, front contact and armature of relay 202 to thepositive pole of battery. Relay 203 on operating, closes a break pointin a locking circuit for itself thru its lower innermost frontcontactand armature, back contact and armature of relay 202 (when this relayreleases) to the positive pole of battery. On the operation of the relay203, the slow releasing relay 204 isoperated in a circuit extending fromthe negative pole 'of battery, front contact and armature of relay 203,front contact and armature of relay 202 to the positive pole of battery.Relay 204 locks itself operated at the armature and front contact ofrelay 202. When the impulse of alternating current terminates, relays20I and 202 deenergize. Relay 202 on releasing, closes the previously'mentioned locking circuit for the relay 203. Relay 204 now has itsenergizing circuit interrupted at the lowermost front contact andarmature of relay 202. With the relay 202 deenergized and with relay 203operated, a circuit is closed across the tip 'and ring conductors of theincoming line circuit. This .causes an idle link circuit to connect withthe line circuit now in use. When this connection is effected theoperator can then proceed to dial the required number. With the dialcit-normal contacts 205 (Fig. 4) closed, the negative pole of battery isconnected thru the low resistance coil 206, off normal contacts 205 andimpulse contacts 201 of the dial, conductor 208, contacts of the dialkey 209, sleeve contacts of the plug P and jack J, conductor I82,winding of relay I and marginal relay I8I, to thepositive pole ofbattery. The marginal relay I8I is operated in this circuit. When theoperator actuates the dial, the circuit last described is opened atthedial impulse springs 201 a number of times corresponding to thenumber dialed. At each interruption of the impulse circuit, caused bythe dial operation, the relays I80 and I8I -are released and. againenergized after the interruptions. At the end-of the dialing operation,the marginalrelay I8I does not energize because the dial off normalcontacts 265 opens the circuit thru the low resistance coil 266 leavinga high resistance circuit including coils 284 and 285, completed thruthe mentioned sleeve contacts. When the relay I8I is thus intermittentlyenergized, it extends a circuit for the slow releasing relay 2H] fromthe negative pole of battery, winding of this relay, front contact andarmature of relay I6I, conductor I15, jack contacts I16 to the positivepole of battery. This circuit holds the slow releasing relay 2H]operated during the series of impulses. However, the relay H is releasedduring the interval between each series of impulses. In response to eachdial impulse, the relay I11 (Fig. 4) is energized in a circuit extendingfrom the negative pole of battery, winding of this relay, conductorarmature and back contact of the ringing relay I16, conductor ZI I,lower front contact and armature of relay 2I6, back contact and armatureof relay I86, conductor I15, jack contacts I16 to the positive pole ofbattery. Therefore, an impulse of alternating current is applied at thefront contacts and armatures of relay I11 at each interruption of theimpulse circuit at the dial impulse springs, which impulse ofalternating current is transmitted over the trunk leading to the dialoffice. Since the slow releasing relay I54 (Fig. 3) is deenergized atthis time, these impulses of current are applied to the rectifyingbridge RB which operates to apply pulsating current corresponding tothese impulses to the relay 26L It will be appreciated that thesepulsations in this rectified current are sufficiently smooth to operatethe relay 20I without chatter and also permit this relay to release atthe end of each impulse period. Relay 20I (Fig. 3) and relay I86 (Fig.4) therefore follow the impulses corresponding to the number designationof the wanted subscriber in the dial office. The relay 262 at its backcontact controls the impulse circuit leading to the link which wasselected. This supplies impulses to the link in accordance with theimpulses received over the trunk circuit. When the link has beenconnected to the line of the wanted subscriber this line is tested forits busy or idle condition and if found idle, ringing current is appliedthereto in the manner previously described. When the called subscriberanswers, the polarized relay 2 (Fig. 3) is energized to close an obviouscircuit for the slow releasing relay 2I2.

When the called subscriber hangs up, relays 2H and 2I2 are released insequence. During the time interval required for the relay 2I2 torelease,a circuit is extended for operating the slow releasing switching relayI54. This circuit is completed from the negative pole of battery,winding of this relay, conductor I55, front contact and armature of slowreleasing relay 2I2, back contact and armature of relay 2II to thepositive pole of battery. However, when relay 2I2 releases the switchingrelay I54 will also release. But during the interval when relay I54 isenergized, alternating current is extended thru the front contacts andarmatures of relay I6I, front contacts and armatures of relay I54 to thewindings of repeating coil I62 and thence by induction over the trunk togive a disconnect signal. The impulse of alternating current actuatesthe alternating current relay I63 (Fig. 4). Since relay I68 is energizedat this time, the relay I9I is energized from the negative pole ofbattery, common coin box tone key I92, lower winding of relay I9I, frontcontact'and arma- '75 ture I61 of relay I68, armature and front contactof relay I63, back contact and continuity spring of relay I64 to thepositive pole of battery. Relay I9I locks itself operated and connectsthe condensers I94 and I in series with the talking conductors of thecord circuit in use. This effects the release of the supervisory relay(not shown) of the cord circuit in use, for giving the operatordisconnect supervision.

The release of the connection from the manual office to the dial ofiiceis indicated by an extra long impulse of alternating current applied tothe trunk circuit. This is accomplished by the release of the relay I68when the operator removes the plug P from the jack J.

It will be recalled that the relay I63 has been maintained energized ina circuit extending from the negative pole of battery, winding of thisrelay, back contact and armature of relay I66, back contact and armatureI14 of relay I64, conductor I15, jack contacts I16 to the positive poleof battery. When the operator releases the connection by removing theplug P from the jack J, contacts I16 are opened. On the release of therelay I68, the slow-to-operate ringing relay I13 is energized at theback contact and armature of relay I68, and the relay I11 is nowoperated from the negative pole of battery, winding of this relay,conductor 2I5, front contact and armature of slow releasing relay 2I6,back contact and armature of relay I68 to the positive pole of battery.It will be understood that when the slow to operate ringing relay I18 isenergized, it opens the operating'circuit of the slow releasing relay2I6. In this interval when relay I18 is operating and relay M6 isreleasing, the relay I11 is operated as described for an extra longinterval due to the delayed action of relays I18 and H6. The operationof relay I11 applies alternating current over the trunk. In response tothis impulse, the rectifying bridge RB functions to operate the relay26I. Relay 2IlI at its inner front contact and armature, completes acircuit which operates the relay 262. When relay 262 operates, it opensits lowermost armature and back contact and thereby interrupts thelocking circuit of the slow releasing relay 203. At the close of theimpulse of alternating current, relays ZIlI and 202 release in sequenceand with the relay 202 deenergized the locking circuit of the slowreleasing relay 263 is opened so that this relay deenergizes. Relay 262was therefore energized for an extra long time interval as described forreleasing the connection to the dial office by holding the line circuitopen for an extra long period of time.

Coin box tone If a subscribers line equipped with a coin box selects atrunk leading to the manual office (Fig. 3), an impulse of coin box tonecurrent is applied to this trunk when the operator answers. The operatorcan also apply ringing current (by means not shown) back over the trunkwhile operating the common coin box key'I 92 for again causing coin boxtone to be momentarily applied to the trunk. In this way an indicationis given to the distant operator when the calling substation is equippedwith a coin box.

This coin box tone is applied to the trunk at the time that the operatoranswers and during the time that the relay I66 (Fig. 3) is released andthe relay I81 is operated. -It will be understood that a stationequipped with a tone box has a coin box tone connection made to the

